Systems and methods for creating arteriovenous (AV) fistulas

ABSTRACT

An AV fistula between first and second blood vessels is created by forming a hole through adjacent walls of the vessels and inserting a welding catheter into the first vessel, and through the hole into the second vessel, so that a distal end of the catheter is disposed within the second vessel. A portion of wall defining the welding catheter is then expanded radially outwardly, and the expanded wall portion is pulled proximally to engage the wall of the second blood vessel and to pull it toward the wall of the first blood vessel. A portion of wall proximal to the first expanded wall portion and disposed in the first blood vessel is expanded radially outwardly, thereby capturing the walls of each of the second and first blood vessels between the two expanded wall portions. Cutting elements are energized to create a tissue welded elongate aperture between the blood vessels.

This application claims the benefit under 35 U.S.C. 119(e) of the filingdate of Provisional U.S. Application Ser. No. 61/480,638, entitledSystems and Methods for Creating Arteriovenous (AV) Fistulas, filed onApr. 29, 2011. It is also related to is related to U.S. application Ser.No. 13/161,182, entitled Systems and Methods for Creating Arteriovenous(AV) Fistulas, filed on Jun. 15, 2011, and U.S. application Ser. No.13/161,356, entitled Intravascular Arterial to Venous Anastomosis andTissue Welding Catheter, filed on Jun. 15, 2011. All of the foregoingapplications are expressly incorporated herein by reference, in theirentirety.

BACKGROUND OF THE INVENTION

In the body, various fluids are transported through conduits throughoutthe organism to perform various essential functions. Blood vessels,arteries, veins, and capillaries carry blood throughout the body,carrying nutrients and waste products to different organs and tissuesfor processing. Bile ducts carry bile from the liver to the duodenum.Ureters carry urine from the kidneys to the bladder. The intestinescarry nutrients and waste products from the mouth to the anus.

In medical practice, there is often a need to connect conduits to oneanother or to a replacement conduit to treat disease or dysfunction ofthe existing conduits. The connection created between conduits is calledan anastomosis.

In blood vessels, anastomoses are made between veins and arteries,arteries and arteries, or veins and veins. The purpose of theseconnections is to create either a high flow connection, or fistula,between an artery and a vein, or to carry blood around an obstruction ina replacement conduit, or bypass. The conduit for a bypass is a vein,artery, or prosthetic graft.

An anastomosis is created during surgery by bringing two vessels or aconduit into direct contact, and to create a leak-free blood flow pathbetween them. The vessels are joined together with suture or clips, inan open surgical procedure. The anastomosis can be end-to-end,end-to-side, or side-to-side. In blood vessels, the anastomosis iselliptical in shape and is most commonly sewn by hand with a continuoussuture. Other methods for anastomosis creation have been used includingcarbon dioxide laser, and a number of methods using various connectingprosthesis, clips, and stents. Such procedures are time consuming,clinician dependent (open to surgical error), and often result instrictures, or clotting of the vein or artery.

An arterio-venous fistula (AVF) is created by connecting an artery to avein. This type of connection is used for hemodialysis, to increaseexercise tolerance, to keep an artery or vein open, or to providereliable access for chemotherapy.

An alternative is to connect a prosthetic graft from an artery to a veinfor the same purpose of creating a high flow connection between arteryand vein. This is called an arterio-venous graft, and requires twoanastomoses. One is between artery and graft, and the second is betweengraft and vein.

A bypass is similar to an arteriovenous graft. To bypass an obstruction,two anastomoses and a conduit are required. A proximal anastomosis iscreated from a blood vessel to a conduit. The conduit extends around theobstruction, and a second distal anastomosis is created between theconduit and vessel beyond the obstruction.

As noted above, in current medical practice, it is desirable to connectarteries to veins to create a fistula for the purpose of hemodialysis.The process of hemodialysis requires the removal of blood from the bodyat a rapid rate, passing the blood through a dialysis machine, andreturning the blood to the body. The access to the blood circulation isachieved with catheters placed in large veins, prosthetic graftsattached to an artery and a vein, or a fistula where an artery isattached directly to the vein.

Fistulas for hemodialysis are required by patients with kidney failure.The fistula provides a high flow of blood that can be withdrawn from thebody into a dialysis machine to remove waste products and then returnedto the body. The blood is withdrawn through a large access needle nearthe artery and returned to the fistula through a second large returnneedle. These fistulas are typically created in the forearm, upper arm,less frequently in the thigh, and in rare cases, elsewhere in the body.It is important that the fistula be able to achieve a flow rate of 500ml per minute or greater. Dialysis fistulas have to be close to the skin(<6 mm), and large enough (>4 mm) to access with a large needle. Thefistula needs to be long enough (>6 cm) to allow adequate separation ofthe access and return needle to prevent recirculation of dialysed andnon-dialysed blood between the needles inserted in the fistula.

To create a fistula, it is necessary to carefully dissect an artery andvein from their surrounding tissue, and to join them to create aleak-free blood flow path between them. This is typically done bysuturing the vein to the artery in an open surgical procedure, usingfine suture or clips. The vein is either attached by an end to endanastomosis, end to side anastomosis, or a side to side anastomosis. Theprocedure is time consuming, clinician dependent (open to surgicalerror), and often times results in strictures, or clotting of the veinor artery. It is highly desirable to be able to make the anastomosisquickly, reliably, with less dissection, and with less pain. It isimportant that the anastomosis is the correct size, is smooth, and thatthe artery and vein are not twisted.

SUMMARY OF THE INVENTION

The present disclosed invention eliminates the above described openprocedures, reduces operating time, and allows for a consistent andrepeatable fistula creation.

It is well known that heat, whether its source is Radio Frequency (RF),resistance, or laser, will attach and weld tissue or vessels upon directpressure and contact over the targeted weld area. This is often donewith jaw-type, compression heat delivery devices. It is also well knownthat radially expandable devices such as balloons, metal cages, andbaskets are often coupled with energy in the form of RF, or in the caseof balloons, heated saline, and used intraluminally to ablate tissue,stop bleeding, or create a stricture.

The present invention uses two pair of opposable, collapsible slits onthe main catheter body that extend outwards and trap with compressionthe surrounding vessel walls between them. Heat is then applied to thetissue using RF energy or resistance heat through the exposed woven wireelements. The woven wire elements are actually a component of thecoaxial wire mesh embedded into the main catheter body. This coaxialmesh serves two purposes. One is to increase the torqueability of themain catheter, and a second is to supply energy to the exposedelectrodes. The electrodes are created by scathing a desired amount ofthe encapsulating layer of polymer over the wire mesh. Heat from thedevice travels internally through the vessel walls to the adventitiawhich surrounds the vessels. With the combination of heat and clampingforce, the vessels are joined together.

More particularly, there is provided a device for creating anarteriovenous (AV) fistula, which comprises a welding cathetercomprising an elongate tube having a circumferential wall. The firstportion of the wall is actuatable between a collapsed orientationwherein the distal portion is axially aligned with remaining portions ofthe circumferential wall and a radially expanded orientation. A secondportion of the wall, spaced proximally from the first wall portion, isactuatable between a collapsed orientation wherein the distal portion isaxially aligned with remaining portions of the circumferential wall anda radially expanded orientation. Tissue cutters are disposed on thecircumferential wall on and adjacent to the first and second portionsthereof. The first wall portion further comprises a plurality ofcircumferentially spaced slots disposed therein, which in one embodimentcomprises a pair of circumferentially opposed slots. The second wallportion also comprises a plurality of circumferentially spaced slotsdisposed therein, which in one embodiment also comprises a pair ofcircumferentially opposed slots.

The first and second portions of the wall are each biased toward theirrespective radially expanded orientations. The elongate tube furthercomprises an axial through hole and an inner tube disposed in the axialthrough hole, wherein the elongate tube and the inner tube are attachedto one another distally of the first and second wall portions. Anactuator is disposed on a handle proximal to the elongate tube, foractuating the first and second wall portions between their radiallyexpanded and collapsed orientations. The actuator has a first positionfor radially expanding only the first portion of the wall and a secondportion for also radially expanding the second portion of the wall. Inthe disclosed embodiments, the actuator functions to actuated theradially expanding first and second portions by pulling the inner tubeproximally.

An outer sheath is axially positionable to cover both of the radiallyexpanding first and second wall portions, and is alternatively axiallypositionable to selectively expose only the first wall portion or bothof the first and second wall portions.

A power source is provided for selectively energizing the tissuecutters, which, in certain embodiments, are energized by RF energy. Inthe illustrated embodiments, the tissue cutters comprise wire meshelectrodes.

In another aspect of the invention, there is disclosed a method ofcreating an AV fistula between adjacent first and second blood vessels,which comprises steps of cutting a hole through the adjacent walls ofthe first and second blood vessels and inserting a welding catheter intothe first vessel, and through the hole into the second vessel, so that adistal end of the welding catheter is disposed within the second vessel.A portion of wall defining the welding catheter is then expandedradially outwardly, and the expanded wall portion is pulled proximallyto engage the wall of the second blood vessel and to pull it toward thewall of the first blood vessel. Then, a portion of wall proximal to thefirst expanded wall portion and disposed in the first blood vessel isexpanded radially outwardly, thereby capturing the walls of each of thesecond and first blood vessels between the two expanded wall portions.Cutting elements on the expanded wall portions are then energized tocreate a tissue welded elongate aperture between the first and secondblood vessels.

An additional method step following the foregoing steps involvescollapsing the first and second expanded wall portions and withdrawingthe welding catheter from the blood vessels. The energizing step, incertain embodiments, comprises energizing electrodes, which may comprisewire mesh electrodes, with RF energy.

The hole cutting step may be performed, in accordance with the inventivemethod, by inserting a needle into the first blood vessel, extending anobturator through a lumen in the needle until a tip thereof contacts thewall of the first blood vessel, and energizing a cutting tip of theobturator to cut the hole.

Preferably, an outer sheath is disposed over an elongate tube comprisingthe welding catheter, and the inventive method further comprises a stepof withdrawing the outer sheath proximally to expose the first wallportion prior to the first expanding step. The method further comprisesa step of withdrawing the outer sheath proximally to expose the secondwall portion prior to the second expanding step.

The invention, together with additional features and advantages thereof,may best be understood by reference to the following description takenin conjunction with the accompanying illustrative drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view showing the first step of an inventivemethod for creating an A-V fistula in accordance with the principles ofthe present invention;

FIG. 2 is a view similar to FIG. 1, wherein a needle has been insertedinto a vessel in the hand of a patient;

FIG. 3 is a view illustrating the insertion of a guidewire through theneedle into the vessel;

FIG. 4 is a view similar to FIG. 3 wherein the needle has been withdrawnand removed;

FIGS. 5-18 are sequential views illustrating one method of utilizing theinventive system;

FIG. 19 is a cross-sectional view of a multilumen catheter andassociated structure;

FIGS. 19 a-19 c illustrate alternative distal work pieces for the needleand associated cutting features of the inventive system;

FIG. 19 d is a cross-sectional view taken through lines A-A of FIG. 19;

FIG. 20 is an isometric view of a welding catheter constructed inaccordance with the principles of the present invention;

FIGS. 20 a and 20 b illustrate a distal portion of the welding catheterof FIG. 20 in sequential modes;

FIG. 21 is a view similar to FIG. 20 b, showing an alternativeembodiment;

FIG. 21 a is an end view of the device shown in FIG. 21;

FIG. 22 is a view similar to FIG. 20 b, illustrating another alternativeembodiment; and

FIG. 22 a is an isolation view showing still another alternativeembodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now particularly to FIGS. 19-22, a particular embodiment of asystem for creating an A-V fistula, in accordance with the principles ofthe present invention, will be described. A welding catheter 10 (FIG.20) comprises, in a presently preferred embodiment, a 3-4 f (French)(70-80 shore A) elongate tube or outer sheath 12, having a through hole14 for accommodating a 2-3 f inner tube 16 and a standard 0.014 diameterguidewire. A distal end 18 is tapered with a softer (40-50 shoreA)polymer tip which is in the range of 1-2 inches in length. This is toallow atraumatic ease of entry into and through the vessels. The innertube 16 is preferably constructed of a flexible material such as apolymer in the range of 70-90 shoreA or a thin-walled nitinol metal. Thedistal end of the main catheter tube 12 features four (4) slots 20, 20a.

The slots 20, 20 a are arranged so that there are two slots 20, 20 a inseries on each side of the tube 12, with each set of two slots 20, 20 aopposed 180 degrees from one another about the circumference of thetube. Thus, there is a set of distal opposed slots 20, and a second setof proximal opposed slots 20 a. The slots 20, 20 a are preferably withina range of 0.030-0.060 inches long, and are biased to be axiallycollapsed, as shown in FIG. 20, when tension is applied to the innertube 16. The inner tube 16 must have enough column strength to activatethe collapsible wings (described below) into their radially expandedorientation when it is pulled proximally. To clarify terminology usedthroughout this application, when the slots are axially collapsed, thewings are radially expanded. Likewise, when the slots are axiallyexpanded, the wings are radially collapsed. The inner 3 f tube 16 isattached to the inner diameter (ID) of the outer 4 f tube 12 near thedistal end. A 4-5 f elongate tube 22 extends over the tube 12 and isslidably attached at the proximal end thereof. The outer tube 12 isattached to a handle 24 at a proximal end 26, and is fixed in place.Wire mesh 28 of the outer tube 12 is exposed, as shown, and a conductorwire 30, preferably in a range of 16-20 Ga. (Gauge) is attached to themesh, as shown, at one end, and has a standard banana connector 32 atthe opposite end for attachment to an RF generator. The inner tube 16 isattached at the distal end by the slidable actuator handle 24. Theactuator handle 24 has two positions. A first position 31 a (FIG. 20),actuates the axial collapse of the distal set of slots 20, so that firstradially protruding wings 34 are formed by expanding radially outwardly,as shown in FIG. 20 a. A second position 31 b (FIG. 20), actuates thefurther collapse of the proximal set of slots 20 a, as shown in FIG. 20b, to form second radially protruding wings 36, proximally of the firstwings 34. These two sets of wings 34, 36, when the slots 20, 20 a arecollapsed, have an expanded width of approximately 3-6 mm. The innertube 16 has a through lumen 38 to allow passage over a guidewire.

Now referring particularly to FIGS. 19, 19 a, 19 b, and 19 c, there isshown a multilumen catheter 40, preferably having a 4-5 f diameter. Acentral lumen 42 accommodates the passage of a standard 0.018 diameterguidewire 44. A second lumen 46 accommodates a pre-bent cannulatedneedle 48, having a 0.015 inside diameter to accommodate a 0.014diameter guidewire. The angle 50 of the bent needle 48 is preferablywithin the range of 30-45 degrees, and includes a removable pencil pointtip obturator 52. The obturator 52 is fabricated of nitinol or othersuitable material, and insulated 54, as shown in FIG. 19 b, with onlythe tip 56 exposed. Heat is applied to the tip 56 from an RF energysource connected to the distal end. The catheter 40 is preferably madeof a polymer in the range of 60-75 shoreA. The needle 48 is preferablymade of nitinol, with an OD in the range of 0.019-0.021. The memorycharacteristics of nitinol allow the needle to deform and nest while inthe catheter lumen. The distal end of the catheter is tapered to allowease of entry into the vessel. FIGS. 19 a, 19 b, and 19 c showalternative obturator designs. FIG. 19 b is the presently preferredembodiment, already discussed above, while FIG. 19 a shows a cold tipwithout RF heat, and FIG. 19 c shows a corkscrew or auger design whichallows traction during penetration into the vessel. The guidewire 44 canbe run through the corkscrew device.

With particular reference now to FIGS. 1-18, to begin the inventivemethod of creating an AV fistula, the practitioner selects anappropriate procedural site having each of a first vessel 58 and asecond vessel 60 in close proximity to one another. In currentlypreferred approaches, the first vessel 58 comprises a vein, and thesecond vessel 60 comprises an artery, but the invention is notnecessarily limited to this arrangement. As illustrated in FIG. 1, onepresently preferred location is the hand 62 of a patient. Then,generally employing principles of the Seldinger technique, as shown inFIG. 2, the first vessel 58 is punctured by a needle 64, which isinserted therein, in the direction of an arrow 66. A first guidewire 68,preferably a standard 0.014 diameter guidewire, is then inserted througha lumen of the hollow needle 64 into the vessel 58, and advanced in thedirection of an arrow 70 (FIG. 3). Following this, as shown in FIG. 4,the needle 64 is removed, by withdrawing it in the direction of an arrow72.

The vessel access catheter 40 is placed over the first guidewire 68 andinserted over the guidewire into the first vessel 58, in the directionof arrow 74, as shown in FIG. 5. As illustrated in FIG. 6, the pre-bentcannulated needle 48 is then extended out of the catheter 40 from a sideport 76 and into contact with the second vessel 60. The obturator (FIG.19) 52, with its cutting tip is extended through the needle 48, and RFenergy is applied to the needle, as shown in FIG. 7, preferably in therange of 10-20 W monopolar, creating a hole in the vessel walls andallowing the needle 48 to extend in the direction of arrow 78 fartherinto the second vessel 60. Then, as shown in FIG. 8, the obturatorcutting element 52 is removed, and the second guidewire 44 is passedthrough the lumen of the needle 48, distally in the direction of arrow80 (FIG. 9). This second guidewire 44 creates the access path for thewelding catheter 10 (FIG. 20). The access needle 48 is retracted in thedirection of arrow 82 (FIG. 10), and the welding catheter 12 is passedover the guidewire 44 distally into the first vessel, and then into thesecond vessel, as shown in FIGS. 11 and 12.

The outer tube or sheath 12 is retracted proximally to expose theunderlying catheter, as shown in FIG. 13, sufficiently to expose thefirst pairs of opposed slots 20. The inner tube 16 (FIG. 20) isretracted by the activation lever 24 to first position 1, therebycausing the first pair of slots 20 to collapse and extend outwardly(FIG. 14). Once locked in place, the catheter is pulled back, causingthe second vessel 60 to come into contact with the first vessel 58 (FIG.15).

At this juncture, the outer sheath 12 is retracted further, to exposethe second set of slots 20 a (FIG. 16). The activation lever 24 is thenretracted from the first position 31 a to the second position 31 b,which causes the second pair of slots 20 a to collapse and extendoutwardly, forming the second radially protruding wings 36, trapping thesurrounding wall of the first vessel and second vessel between them(FIG. 16). RF energy is then applied, and the mesh electrodes 28 on bothextended members create the weld between the first and second vessels.More particularly, the RF energy functions to burn and fuse or weld thevessels together, creating an elongate aperture 84 through the opposingwalls of each of the first vessel 58 and second vessel 60, as well asany intervening tissue. This elongate aperture 84 is shown in FIGS. 17and 18. Alternative cutting approaches, such as resistive heat (hotwire), ultrasonic, laser, or mechanical approaches, may be used insteadof RF energy, if desired. The wings 34, 36 are then collapsed byreturning the activation lever 24 back to its original position, and thecatheter 12 is removed (FIG. 17).

As formed, the elongate aperture 84 will typically resemble a slit.However, as pressurized flow 86 (FIG. 18) begins to occur through theslit or aperture 84, which creates a communicating passage between thefirst vessel 58 and the second vessel 60, the aperture widens responsiveto the pressure, taking the shape of an ellipse as it opens to form thedesired fistula. The edges of the aperture are cauterized and welded.

Tissue welding of the type intended to occur in the practice of theseinventive methods is discussed in U.S. Pat. No. 6,908,463, to Treat etal., which is herein expressly incorporated by reference, in itsentirety.

FIGS. 21, 21 a, 22, and 22 a illustrate alternative configurations ofthe inventive device. In FIGS. 21 and 21 a, multiple slots areillustrated for forming multiple wings 34, which may be four, six, oreight. Coated wire expandable mesh tubing to form two conformable cones88, with the internal facing surfaces exposed to create an electrode(FIG. 22). FIG. 22 a illustrates that the RF energy source may also bebipolar, which localizes the heat and welded area.

In yet another unillustrated embodiment, two pair of opposable slits maybe mounted on separate coaxial elongate bodies. The second coaxial bodywith a pair of collapsible slits allows for a predetermined force orpressure on the tissue that is to be welded. This force can be either bymanual operator “feel” or by use of a spring or tensioning means. Thespring tension can also be manually manipulated by rotating the housing,which will vary the compressive spring force, thus allowing the operatorto “tune” the compression or force depending on the distance andcomposition of fat and tissue between the artery and vein.

In still another unillustrated embodiment, the slits on the coaxialbodies are positioned 90 degrees apart. This arrangement in a bipolarmode allows for the dispersion of energy equally around thecircumference of the anastomosis thus creating a symmetrical weld. Theslits on the first body will house the electrode for the first pole andthe slits on the second body with house the electrode for the secondpole.

In another embodiment, the second coaxial body is a coaxial tube with ancircumferential electrode exposed only at the distal end.

Alternative configurations of the mounting of the electrodes on thecollapsible slits are possible, wherein the electrodes are comprised ofround or square stainless steel or nitinol wires in the range of0.002-0.015 diameter communicated to the openings in the expanded slitsthrough lumens in the elongate bodies. This configuration also allowsfor the electrodes to be in the bipolar configuration without having tobe on separate coaxial bodies. A singe electrode may be exposed alongthe length of the expanded slit. Multiple parallel electrodes, may beutilized, wherein the electrodes are exposed as segmented paralleldiameters. This configuration may also comprise staggered squares,rectangles or ovals, depending on the desired weld and associatedvessels to be welded. Various electrode configurations can be attachedat the proximal end and sequenced by use of a microprocessor orswitching means. The electrodes are configured in opposable pairs toallow one pair to weld tissue until a predetermined resistance orimpedance is recognized, the pair of electrodes will then shut off andthe second pair is energized until the impedance or resistance levelagain reaches the predetermined amount and then this pair will shut off.This can be repeated for a multiple of electrodes. This will allow forcontrolled welding of the tissue and limit potential charring andnecrosis at the weld site.

Accordingly, although an exemplary embodiment and method according tothe invention have been shown and described, it is to be understood thatall the terms used herein are descriptive rather than limiting, and thatmany changes, modifications, and substitutions may be made by one havingordinary skill in the art without departing from the spirit and scope ofthe invention.

What is claimed is:
 1. A device for creating an arteriovenous (AV)fistula, comprising: a welding catheter comprising an elongate tubehaving a circumferential wall; a first portion of said wall beingactuatable between a collapsed orientation wherein said first wallportion is axially aligned with remaining portions of saidcircumferential wall and a radially expanded orientation, the first wallportion further comprising a plurality of circumferentially spaced slotsdisposed therein; a second portion of said wall, spaced proximally fromsaid first wall portion, which is actuatable between a collapsedorientation wherein said first wall portion is axially aligned withremaining portions of said circumferential wall and a radially expandedorientation; and tissue cutters disposed on said circumferential wall onand adjacent to said first and second portions thereof.
 2. The device asrecited in claim 1, wherein said plurality of circumferentially spacedslots comprises a pair of circumferentially opposed slots.
 3. The deviceas recited in claim 1, wherein said second wall portion furthercomprises a second plurality of circumferentially spaced slots disposedtherein.
 4. The device as recited in claim 3, wherein said secondplurality of circumferentially spaced slots comprises a pair ofcircumferentially opposed slots.
 5. The device as recited in claim 3,wherein said first and second portions of said wall are each biasedtoward their respective radially expanded orientations.
 6. The device asrecited in claim 1, wherein the elongate tube further comprises an axialthrough hole and an inner tube disposed in said axial through hole, saidelongate tube and said inner tube being attached to one another distallyof said first and second wall portions.
 7. The device as recited inclaim 6, and further comprising an actuator disposed on a handleproximal to said elongate tube, for actuating said first and second wallportions between their radially expanded and collapsed orientations. 8.The device as recited in claim 7, wherein said actuator has a firstposition for radially expanding only the first portion of said wall anda second portion for also radially expanding the second portion of saidwall.
 9. The device as recited in claim 8, wherein said actuatorfunctions to actuate said radially expanding first and second portionsby pulling said inner tube proximally.
 10. The device as recited inclaim 8, and further comprising an outer sheath which is axiallypositionable to cover both of said radially expanding first and secondwall portions, and is alternatively axially positionable to selectivelyexpose only the first wall portion or both of the first and second wallportions.
 11. The device as recited in claim 1, and further comprising apower source for selectively energizing said tissue cutters.
 12. Thedevice as recited in claim 11, wherein said tissue cutters are energizedby RF energy.
 13. The device as recited in claim 11, wherein said tissuecutters comprise wire mesh electrodes.